public class Extend01 {
    public static void main(String[] args){
        int year = 20,num = 60;
        int sumSingle = 0;

        for(int i = 1;i <= year;i++){
            sumSingle += i;
        }

        int sum = sumSingle * num;
        System.out.println(num + "人一共能种" + sum +"棵树");
    }
}
